According to Singer's Application of Environmental Value Theory, Why Does

According to Singer's application of environmental value theory, why does the life of a dog have less moral value than that of a typical human?

A) The dog does not fear death and his death produces less sorrow for those that love him than a human death.
B) The dog experiences pain without understanding it and has no conception of life after death.
C) The dog contributes less to society than a human and is incapable of feeling empathy for those around him.
D) The dog is primarily driven by instinct rather than morals and cannot reason through his actions.